1. Field of the Invention
This invention relates to an image forming apparatus of the type in which a carriage for carrying an original image is moved reciprocally over an optical system and more particularly relates to novel carriage mounting and drive arrangements which facilitate opening the apparatus for repair or replacement of parts.
2. Description of the Related Art
U.S. Pat. Nos. 4,500,195, 4,538,896, 4,588,280 and 4,609,276 and Japanese Utility Model Laid Open Application No. 52-54633 disclose image formation devices, such as electrophotographic copying machines, which have a moveable carriage for reciprocally moving a document to be copied in a horizontal direction over a scanning slit in the body of the machine. The bodies of the machines shown in these patents are divided into an upper body portion and a lower body portion and the upper body portion swings to from the lower body portion, like the opening of a clamshell, to provide access to the internal mechanism of the machine for cleaning, adjustment or repair, or to free jammed paper.
In the above identified U.S. patents the moveable carriage is mounted on the upper body portion; and therefore the carriage and its supporting and driving mechanism must be swung up together with the upper body portion when the machine is opened. Because of this the upper body portion must be large and of heavy construction; and a large spring or other actuating means must be provided for opening and holding the upper body portion in its opened position. The Japanese Utility Model shows a copying machine having a moveable carriage and an optical system mounted in the main body portion. Only the photosensitive drum of this copying machine is mounted on the second or moveable body portion. This means that when the moveable body portion is swung upwardly, it provides very little access to the internal components.
In addition, these known image forming apparatus of the type shown in the above-mentioned U.S. patents and Japanese Utility Model suffer from the following disadvantage. Namely, in these known apparatus, there is a risk that the carriage accidentally moved when the apparatus is in the open state, due to an erroneous operation of the carriage driving system of the apparatus.